Abstract. Investigation of the switching phenomenon in single crystal TlInS 2 revealed that it is typical for a memory switch. The switching process takes place with both polarities on the crystal and have symmetrical shapes. Current-voltage characteristics (CVC) of symmetrical Ag/p-TlInS 2 /Ag structures exhibit two distinct regions, high resistance OFF state and low-resistance ON state having negative differential resistance (NDR). TlInS 2 is a ternary semiconductor exhibiting S-type i-v characteristics. The results strongly indicate that the phenomenon in our sample is very sensitive to temperature, light intensity and sample thickness. The switching parameters were checked under the influence of different factors of the ambient condition.